As this type of anti-vibration apparatus, hitherto, an anti-vibration apparatus having the following structure has been known. The apparatus includes a cylindrical first mounting member connected to one of a vibration generating portion and a generation receiving portion, a second mounting member connected to the other of the vibration generating portion and the vibration receiving portion, and a first rubber elastic body for elastically connecting the first and second mounting members to each other. Furthermore, an inner part of the first mounting member is divided into a primary liquid chamber and a secondary liquid chamber by a dividing member. The primary liquid chamber is configured such that a liquid is sealed therein making the first rubber elastic body part of the partition wall and an inner volume thereof is changed due to the deformation of the first rubber elastic body. The secondary liquid chamber is configured such that at least one part of the partition wall is formed in a deformable manner and the liquid is sealed therein. In addition, between an outer peripheral surface side of the dividing member and an inner peripheral surface side of the first mounting member, an orifice passage for linking the primary liquid chamber with the secondary liquid chamber is formed and the liquid is sealed in the primary liquid chamber and the secondary liquid chamber.
In the anti-vibration apparatus, hitherto, after a large vibration (load) has been input due to undulations of a road surface or the like and a liquid pressure of the primary liquid chamber has risen rapidly, for example, when the vibration is input in a reverse direction due to a rebound of the first rubber elastic body or the like, the primary liquid chamber may become a negative pressure. At this time, cavitation is generated in which a plurality of bubbles is produced in the liquid within the primary liquid chamber. Then, when the bubbles dissipate from the liquid along with an increase in the liquid pressure within the primary liquid chamber, a shock wave is generated. The shock wave is diffused to a metallic material such as the first mounting member or the like, which generates an abnormal noise.
As a means for preventing the occurrence of the abnormal noise, as described in Patent Document 1 described below, for example, there is a known structure in which a linking hole for linking the primary liquid chamber with the secondary liquid chamber is formed in the dividing member separately from the orifice passage and a valve is provided in the linking hole. In the apparatus having this structure, after the liquid pressure of the primary liquid chamber has risen rapidly, when a negative liquid pressure would be generated, due to the opening of the valve and the short-circuiting of the primary liquid chamber and the secondary liquid chamber, a decline in the liquid pressure of the primary liquid chamber is suppressed and the occurrence of the cavitation is prevented in advance.
[Patent Citation 1] JP-A 2003-148548